5.1: Gallery Library Card Catalogs , circa 1904-circa 1977
At the beginning of the Card Catalog I are four index cards that explain the firm's filing system: books were generally filed under subject and author; exhibitions were filed by country, city, gallery, museum, or subject; private collections were filed under "Collections"; exhibition catalogs of individual collections were filed under the collector's name; auction sales were sometimes listed by subject; the category "Dictionaries" gave listings of general reference works; and "General" listings were books that did not fit other classifications. In Card Catalog II many of the entries reference exhibition or auction catalogs.
5.1.1: Card Catalog I, circa 1904-circa 1971
5.1.2: Card Catalog II, circa 1925-circa 1977